The invention relates to a method of fabricating a protective film having moisture-proof performance.
In the fabrication of a semiconductor integrated circuit, an insulating film made from SiO2 etc., and a protective film made of a nitride film made from Si3N4 etc. are generally formed by the plasma CVD (Chemical Vapor Deposition) method (refer to patent document, for example, JP, H 11-214670, A) or a thermal CVD method such as the LP (Low Pressure) CVD method, and so forth. For example, the nitride film made from Si3N4 is formed by the LP CVD method carried out at a high reaction temperature in the range of 800 to 900° C. by use of dichlorosailane gas and ammonia gas as stock gases. Incidentally, the following U.S. applications for Letters patent relating to a method of fabricating an insulating film by use of vacuum ultraviolet rays, which are commonly assigned with this application, have been submitted to U.S. PTO by the assignee of the inventor of this application: Ser. Nos. 09/798,930, 09/833,646, 10/052,243, 10/059,174, and 10/105,382.
If the insulating film and protective film are formed by the plasma CVD method or by the thermal CVD method, this will cause damage to the semiconductor integrated circuit. Such damage is damage sustained by a semiconductor device, caused by expansion of diffusion layers, occurring at a high reaction temperature at the time of carrying out the thermal CVD method, or by the agency of charged particles in plasma at the time of carrying out the plasma CVD method.
As a result of further progress made in miniaturization of the semiconductor integrated circuit, for example, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) formed in the semiconductor integrated circuit undergo a change in construction such that a gate length becomes shorter, and the diffusion layers, such as a channel, etc., become narrower in width as well as shallower in depth. Accordingly, in the case of a miniaturized semiconductor integrated circuit, the above-described damage becomes an increasingly serious problem that must be resolved.